1. Field of the Invention
The present invention relates to a transformer and more particularly to a transformer that can be mounted to a circuit board to form a combination of the transformer and the circuit board with a thin thickness.
2. Description of the Related Art
Nowadays, electronic products have become much thinner and smaller, so the electronic elements for those electronic products have to be manufactured as small as possible. To satisfy the technical requirements, some integrated-circuit elements like transistors can be minimized by advanced semiconductor technologies. Passive circuit elements like resistors and capacitors can be made into smaller ones through advanced packaging technology or using some thinned substrate. However some elements are unable to be manufactured into smaller ones.
Taking a transformer as an example, the transformer converts electrical energy, transfers electrical energy from one circuit to another circuit and is often mounted on a circuit board. In order to provide enough voltage and current value, the turns of the windings of a transformer cannot be reduced. Therefore, the way to reduce the size is to modify the packaging structure. With reference to FIG. 7, as disclosed in Taiwan Utility Model Patent No. M290607, a conventional transformer (50) with multiple connecting pins for circuits connection is mounted on a circuit board (60). The transformer (50) comprises a bobbin (51), a magnetic core assembly (52) to which the bobbin (51) is coupled, and a base (53) on which the magnetic core assembly (52) is mounted. A coil assembly (511) is wound around the bobbin (51). A terminal seat (54) with multiple connecting pins extends from the lower edge of the bobbin (51). The connecting pins (541) protrude perpendicularly from the terminal seat (54) for electrically connecting to the ends of the coil assembly (511). When mounting the transformer (50) on the circuit board (60) to form a transformer assembly, the connecting pins (541) will be respectively inserted into soldering holes defined on the circuit board (60) and soldered. It is noted that the thickness of an electronic product having this transformer assembly will include the thickness of the transformer (50) and the circuit board (60), and reducing the size of this electronic product is difficult.
With reference to FIG. 8, as disclosed in Taiwan Utility Model Patent No. 512968 a bobbin (70) for a conventional surface-mounted (SMT) transformer is manufactured in a relatively flat shape. The bobbin (70) has a bottom. A coil assembly can be wound around the bobbin (70). Multiple flat connecting pins (71) transversely extend out from the opposite sides of the bottom and connect to the ends of the coil assembly. Each of the flat connecting pins (71) has a flat surface to be soldered on a solder pad of a circuit board. Because the bobbin (70) is a flat shape and can be attached to a circuit board by Surface Mounted Technology (SMT), the thickness of electronic product with the transformer can be reduced.
When either of the forgoing transformers is mounted on the circuit board, the entire thickness of the transformer assembly will inevitably include the thickness of the circuit board. Therefore electronic products using either one of the conventional transformer assembly are still thicker than desired.
To overcome the shortcomings, the present invention provides a transformer to mitigate or obviate the aforementioned problems.